N = int(input())
Gnum = [0] * (N + 1)
edge = []
G = [[] for _ in range(N+1)]
for _ in range(N):
    a,b = map(int,input().split())
    Gnum[a] += 1
    Gnum[b] += 1
    edge.append((a,b))
    G[a].append((b,_+1))
    G[b].append((a,_+1))

ans = set(range(1,N+1))
top = []
for i in range(1,N+1):
    if Gnum[i] == 1:
        top.append(i)
        Gnum[i] -= 1
while top:
    now = top.pop()
    for v,index in G[now]:
        Gnum[v] -= 1
        ans.discard(index)
        if Gnum[v] == 1:
            Gnum[v] = 0
            top.append(v)
print(len(ans))
print(*sorted(ans))